<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:padding="16dp"
 tools:context="com.lindroid.countdowndemo.MainActivity">

 <Button
  android:id="@+id/btn_captcha"
  android:layout_width="match_parent"
  android:layout_height="50dp"
  android:background="#c7c7c7"
  android:text="获取验证码"
  android:textAllCaps="false"
  android:textColor="@android:color/black"
  android:textSize="18sp" />

</RelativeLayout>

 private CountTimer countTimer;

 /**
  * 点击按钮后倒计时
  */
 class CountTimer extends CountDownTimer {

  public CountTimer(long millisInFuture, long countDownInterval) {
   super(millisInFuture, countDownInterval);
  }

  /**
   * 倒计时过程中调用
   *
   * @param millisUntilFinished
   */
  @Override
  public void onTick(long millisUntilFinished) {

  }

  /**
   * 倒计时完成后调用
   */
  @Override
  public void onFinish() {

  }
 }

CountTimer countTimer = = new CountTimer(10000, 1000);

 @Override
 protected void onDestroy() {
  super.onDestroy();
  countTimer.cancel();
 }

 CountTimer countTimer = new CountTimer(10000, 1000);

 /**
  * 点击按钮后倒计时
  */
 class CountTimer extends CountDownTimer {

  public CountTimer(long millisInFuture, long countDownInterval) {
   super(millisInFuture, countDownInterval);
  }

  /**
   * 倒计时过程中调用
   *
   * @param millisUntilFinished
   */
  @Override
  public void onTick(long millisUntilFinished) {
   Log.e("Tag", "倒计时=" + (millisUntilFinished/1000));
   btnCaptcha.setText(millisUntilFinished / 1000 + "s后重新发送");
   //设置倒计时中的按钮外观
   btnCaptcha.setClickable(false);//倒计时过程中将按钮设置为不可点击
   btnCaptcha.setBackgroundColor(Color.parseColor("#c7c7c7"));
   btnCaptcha.setTextColor(ContextCompat.getColor(context, android.R.color.black));
   btnCaptcha.setTextSize(16);
  }

  /**
   * 倒计时完成后调用
   */
  @Override
  public void onFinish() {
   Log.e("Tag", "倒计时完成");
   //设置倒计时结束之后的按钮样式
   btnCaptcha.setBackgroundColor(ContextCompat.getColor(context, android.R.color.holo_blue_light));
   btnCaptcha.setTextColor(ContextCompat.getColor(context, android.R.color.white));
   btnCaptcha.setTextSize(18);
   btnCaptcha.setText("重新发送");
   btnCaptcha.setClickable(true);
  }
 }

  public void onTick(long millisUntilFinished) {
   //处理后的倒计时数值
   int time = (int) (Math.round((double) millisUntilFinished / 1000) - 1);
   btnCaptcha.setText(String.valueOf(time)+"s后重新发送");
   //设置倒计时中的按钮外观
   btnCaptcha.setClickable(false);//倒计时过程中将按钮设置为不可点击
   btnCaptcha.setBackgroundColor(Color.parseColor("#c7c7c7"));
   btnCaptcha.setTextColor(ContextCompat.getColor(context, android.R.color.black));
   btnCaptcha.setTextSize(16);
  }

   int time = (int) (Math.round((double) millisUntilFinished / 1000) - 1);
   //拼接要显示的字符串
   SpannableStringBuilder sb = new SpannableStringBuilder();
   sb.append(String.valueOf(time));
   sb.append("s后重新发送");

   //字符“后”在字符串中的下标
   int index = String.valueOf(sb).indexOf("后");
   //给秒数和单位设置蓝色前景色
   ForegroundColorSpan colorSpan = new ForegroundColorSpan(ContextCompat.getColor(context, android.R.color.holo_blue_dark));
   sb.setSpan(colorSpan, 0, index, Spannable.SPAN_INCLUSIVE_EXCLUSIVE);
   btnCaptcha.setText(sb);